Removing benzene from aqueous muriatic acid using a liquid paraffin



INVENTORS KYLE W. RESH BY JACK N. YARBROUGH ATTORNEY United States Patent O 3,445,197 REMOVING BENZENE FROM AQUEOUS MURI- ATIC ACID USING A LIQUID PARAFFIN Kyle W. Resh, Rosedale, Md., and Jack N. Yarbrough,

Wilmington, Del., assignors to Continental Oil Company, Ponca City, Okla., a corporation of Delaware Filed May 27, 1966, Ser. No. 553,452 Int. Cl. B01f 9/02, 9/00 U.S. Cl. 23-312 11 Claims ABSTRACT OF THE DISCLOSURE A method for removing benzene impurities from an aqueous hydrogen halide solution resulting from such processes as alkylation of aromatics. The benzene is extracted in the liquid phase from the aqueous solution using a liquid aliphatic parain or cycloparain or their halogenated homologues.

This invention relates to removal of aromatics from muriatic (hydrochloric) acid. In one of its aspects, thiS invention relates to the recovery of high purity muriatic acid luy-product from alkylation of benzene with chlorinated parafns.

It is known in the art to alkylate aromatics such as benzene with haloparatins, particularly chloroparafiins, to form phenylalkanes. In general, these alkylates are formed from monochlorinated parains of to 14 carbon atoms since such alkylates are particularly useful as intermediates for detergents; however, broadly speaking, such alkylates can be prepared from chloroparains generally. The aromatics, particularly benzene, will attach to the parain by replacing the Cl and giving up HCl as a by-product Some benzene will remain unreacted and will leave the system with the HCl. This HC1 is frequently recovered as muriatic acid by passing the gases into demineralized water. Unfortunately, benzene is also slightly soluble in water and such acids are not suitable for many uses. To remove the benzene, it has been the practice to contact the off gas with a countercurrent flow of chloroparaiiins to remove a substantial portion of the benzene and pass the chloroparaiins to the alkylation step. The HCl gases, still containing some benzene, is then passed through a bed of absorbent, such as activated charcoal, to remove the remaining benzene. The HCl is then adsorbed in water to form muriatic acid.

The above system has at least two disadvantages. First, the chloroparaflins treatment leaves a substantial amount of benzene in the HC1 gas, thus limiting the effective life of the charcoal in the adsorber, More seriously, the adsorption is exothermic and when a freshly charged adsorber is put on stream, extremely high temperatures are reached and since the charcoal cannot be fully stripped of adsorbed oxygen, a fire hazard is created. In fact, it is well known that several such res have resulted from this treatment.

It is, therefore, an object of this invention to provide a means of removing aromatics from muriatic acid.

Another object of this invention is to provide a safe means of recovering high purity halogen acid as a byproduct from alkylation of aromatics with a halogenated paran.

Another object of this invention is to provide a method of recovering high purity muriatic acid from the alkylation of benzene with a chloroparain.

These and other objects of this invention are broadly obtained by contacting an aqueous solution of the haloacid contaminated with an aromatic hydrocarbon with a paraflin or halogenated parain.

AS has been indicated, this invention is applicable to 3,445,197 Patented May 20, 1969 ICC aqueous solutions of a hydrogen halide such as HCl, HF, HI, and HBr. These gases are soluble over a wide range and can be supersaturated. However, we are particularly concerned with aqueous solutions up to the Saturation point.

The aromatic contaminants would include benzene, naphthalene, alkyl substituted benzene and naphthalene such as toluene, methyl-3 ethyl benzene, methyl naphthalene, methyl, 4-butyl naphthalene and the like. Primarily, benzene is the contaminant most often found, and iS somewhat more soluble than these other aromatics in Water.

Of the aliphatic parains which are useful, we prefer those having at least 6 carbon atoms since these are insoluble in water. Preferably, We use normal parains of 10 to 14 carbon atoms since these are the ones of primary interest in alkylation; however, any liquid paraffin will be operable. The paraifn can be branched chain or cy clic. Thus, the operable paratiin would include hexane, octane, nornane, decane, dodecane, tridecane, tetradecane, pentadecane, 3-methyl hexane, 2methyl pentane, 4-butyl octane, 2,-4-dimethyl heptane,2methyl4 ethyl oxane and the like. Of the cycloparaffins we can use, any cycloparaffin which is liquid at the operating conditions, but we generally prefer cyclohexane since it is readily available. Although cyclopropane, cyclohexane, cycloheptane and the like are operable.

As has been mentioned, these paraiins can be halosubstituted; however, again we prefer the monochloro-nparatiins containing 10 to 14 carbon atoms, eg., 2- chlorodecane, 4chloroundecane, 5chlorododecane, -chlorotridecane, 7chlorotetradecane and the like Similar halogenated parains with such halogen as iodine, fluorine, and bromine are also operable as are halogenated cycloparains and isoparafns of the class previously mentioned.

As will be obvious to one skilled in the art, the effectiveness of the treatment will be somewhat dependent upon temperature and volume ratio of solvent to acid. It should also be obvious that the degree of agitation, or rather surface interface contact, is very important. That is, the greater the interface surface, the better the separation. On the other hand, we have found that excessive agitation promotes foaming and emulsions. These emulsions are not stable and will break down upon standing. It the agitation required to effect separation is particularly severe, then holding vessels can be employed to allow suflicient time for the emulsion to break. In general, we prefer a solvent to acid ratio from 1:4 to 1:1; however, greater or lesser amounts of solvent to acid can be used.

While it is possible to remove all of the aromatic from the acid in the paratn con'tact step, the volume ratio of parains `to acid would necessarily be high and the residence time prolonged, or additional contact stages would be required. Therefore, we prefer to lower the aromatic content in this step to 10 to 20 parts per million parts of acid vand remove this final aromatic content by passing the acid over a selective absorbent such as zeolite, silica gel or the like and preferably activated charcoal. It is, of course, within the scope of the invention to reactivate the charcoal by selective desorbing, steam stripping or heat treatment.

The invention will be further described with reference F to the figures of which:

The figure is `a `schematic flow diagram incorporating this invention in the recovery of HC1 from an alkylation process.

In the drawings, valves, heaters, instruments, coolers, pumps and the like yare omitted since all of this is part of the -prior art. In the benzene adsorber, reux cau be employed if desired. It could be a tray tower, packed bed, or any suitable vessel lfor :contactiing the streams. Where a gas stream contacted with a liquid, Ia sparger introdudcing the gas in ine streams can be employed. The acid-paraffin contacting vessel can be of any -suitable type, such as agit-ated vessels, packed towers, spray towers, or tray towers.

Referring now to the figures, a stream comprising alkylate'd benzene, H'Cl an'd unreacted benzene from alkylation unit (not shown) is passed via conduit 4 to benzene adsorber 5 wherein this gas is `countercurrently contacted with liquid n-parains or chloroparain introduced via conduit 6. The n-parafiins (or chloroparaiiins, we will use n-paraiins in this description) will remove part of the benzene and is removed via conduit 7 and sent to the alkylation section '(not shown). The HCl still containing some Ibenzene is taken overhead via conduit 8 and is passed to muriatic acid HC1 adsorber 9. Alternatively, the HCl-benzene stream to adsorber '5 can be passed directly to the muriatic acid vessel 9 via conduit 10 and by opening and closing valves to direct the flow. In either case, a demineralized water is passed into vessel 9 via conduit 11 `and reacts with the HC1 to form hy'drochloric acid, land this acid is diluted to the desired strength with additional water to form the muriatic acid. The mur-iatic acid will absorb `at least a portion of the 4benzene, generally in the range 100-200 p.p.m. based on the acid `and is passed via :conduit 13 to surge drum 25. Any unabsorbed benzene can be bled o via conduit 12 and returne'd to benzene storage (not shown). The benzene contaminated acid is passed via conduit 13a to vessel 14 wherein it is dispersed in n-paraiiins introduced to the vessel via conduit 15. The contacting is aided by means of agitation 16 driven via motor 17. The stream then passes to the separator 26 via conduit 27. The normal parafns will reduce Vthe benzene content of the ac-id down to 10-20 p.p.m. and the n-parains with the absorbe'd benzene passes via conduit 18 to storage. The muriatic acid, now containing less 'than about 20 p.p.m. of benzene is withdrawn from separator 26 and passed via conduit 22 to activated charcoal 'adsorber 23 wherein the charcoal will remove substantially all of the remaining benzene. The rnuriatic lacid containing less than about 1 p.p.m. benzene is removed from vessel 23 via conduit 24 `and sent to storage (not shown). Alternatively, the benzene contaminated muriatic acid from the surge 4drum 4 Example I Plant produced 20 B. hydrochloric acid was saturated with benzene and diluted with additional 20 B. acid to a nal acid containing 265 parts benzene per million parts acid.

Equal parts of the -acid and ya mixture to C12-C14 parains (lzl) were added to va large globe-type `separatory funnel. The mixture was stirred for 5 minutes and then the contents allowed to stand 15 minutes. A small sample of the acid layer was removed -for org-anic analysis and the results -are shown as 1st extract-ion in Table I. The contents were `again stirred for 5 minutes and then allowed to stand again for 15 minutes. A sample of acid was removed for organic analysis and the results are shown yas 2nd extraction in the table. This was repeated for the third time and the organic analysis is reported as 3rd extraction in the table.

TAB LE I Other Benzene hydrocarbons Paradn extraction sample (p.p.m.) (p.p.m.)

Starting acid 265 None 1st extraction 0.14 0. 46 2nd extraction 0. 12 None 3rd extraction. 0. 12 N one This data shown in Table I clearly shows that paraflns will extract benzene from muriatic acid.

Example II TABLE II Analysis of the benzene-spiked 20 Be acid before Analysis of acid after extraction, Benzene conparaffin extraction at 76 F., p.p.m. by wt. p.p.m. by w tent of paratn after extrac- Parathns B Parafns tion, wtf; Benzene enzene percen Cio C11 C1: Cro Cu Cu benzene 0.12 0.4 5.3 0.6 0.5 1.0 0.02 0.02 0.57 0.67 3.3 0.6 0.6 2.2 0.04 Trace 3 .4 0 .4 0 .6 1 .3 0 .06 Trace 4 .6 0.1 0 .4 1 .6 0 .12 0.2 11.9 0.2 1.2 1.8 0.28 747 Trace 21 .3 0 .1 0 .8 1 .5 0 57 TABLE III Analysis of acid after extraction, p.p.m. by wt. Benzene con- Analysis oi the benzene tent of paran spiked 20 Be acid before Paraffius after extracparaftu extraction at tion, wt. per- 125 F., p.p.m. by wt. Benzene Cio Cn C12 cent benzene can be contacted with `a chloroparain of the type to be used in `alkylation in lieu of n-paraiins andthe chloroparain containing adsorbed benzene withdrawn from separator 26 via conduit 18 is sent directly to storage.

Examples To further describe our invention, the following examples are given.

From the above tables, 1t can be seen that the temperature had little elect on benzene extraction.

Example III TAB LE IV Organics in acid phase Volume Benzene, Paratlins Run Volume acid parains p.p.m. p.p.m.

4 1 17 Trace 2 1 12 Trace 1 1 7 Trace From Table 1V, it can be seen that increasing the paradin to acid ratio improves the separation.

Example 1V A plant scale run was made wherein the HCl-benzene from the alkylation units was rst contacted with the chloroparain feed and the HCl-benzene then adsorbed in demineralized water to produce muriatic acid which upon analysis showed 162 p.p.m. benzene, 37 p.p.m. C9, 417 p.p.m. C10, 403 p.p.m. C11, 103 p.p.m. C12 and 2 p.p.m. C13 paraftins, all parts being weight parts based on the acid. This acid was fed into the top of a contact vessel, not packed, and C-C13 parati-ins were sparged into the bottom of the tower. The paraiiins were removed from the top of the separator and the extracted muriatic acid was removed from the bottom of said separator. This acid analyzed 5.5 p.p.m. benzene, 3 p.p.m. C9, 75.8 p.p.m. Cm, 226.8 p.p.m. C11, 231.9 p.p.m. C12 and 64 p.p.m. C13 panaftins. The acid was then percolated through an activated charcoal bed and analyzed less than 0.2 p.p.m. total organics and less than 0.1 p.p.m. benzene.

This example `clearly shows that muriatic acid can be cleaned by iirst contacting same with paraiiins and subsequently cleaning up with charcoal. While it is possible to clean up the acid without tirst extracting with a paratlinic material, the eiective life of the activated charcoal can be greatly increased by iirst reducing the benzene content by extuaction.

While the invention has been described in terms of removing benzene from muriatic acid with a normal aliphatic parain, the method illustrated is broadly applicable to removing aromatics from halogen acids with any oi the panaiiins and/or halogenated paraiiins as disclosed supra.

Having thus described the invention, We claim:

1. A method of removing benzene impurities from a liquid aqueous solution of :a hydrogen halide which comprises contacting said liquid aqueous acid solution with an extraction liquid selected from the group consisting of aliphatic parains land cycloparains of at least 6 carbon atoms, and such parains or cycloparaffins having a halogen substituent thereon and separating the aqueous acid phase from the oil phase.

2. The method of claim 1 wherein the volume ratio of said acid to said extraction liquid being in the range 1:1 tl) 4:1.

3. The method of claim 1 wherein said acid is muriatic acid.

4. The method of claim 3 wherein the volume ratio of muriatic acid to extraction liquid is in the range of 1:1 to 4:1.

5. The method of claim 4 wherein said extraction liquid is a normal paratiin.

6. The method of claim 5 wherein the aqueous phase is subsequently contacted with an adsorbent effective for the adsorption of residual benzene.

7. The method of claim 6 wherein said adsorbent is activated charcoal.

8. The method of claim 4 wherein said extraction liquid is a monochloroparaiin.

9. The method of claim 8 wherein the liquid aqueous acid phase is subsequently contacted with an adsorbent.

10. The method of claim 9 wherein said adsorbent is activated charcoal.

11. The process of recovering by-product HC1 from alkylation of benzene with a chlorinated paraiiin which comprises separating said by-product HC1 and unreacted benzene from product, contacting said by-product HC1 and unreacted benzene with feedstream of said chlorinated paraiins, thereby removing a portion of said benzene, dissolving the HC1 and remaining benzene in demineralized water to lform muriatic acid having benzene dissolved therein, the improvement comprising contacting said muriatic acid with a liquid aliphatic parain of at least 6 carbon atoms thereby removing additional benzene, separating the aqueous muriatic acid phase from the oil phase, and passing the thus separated muriatic acid over `activated :charcoal to remove substantially all of the remaining benzene.

References Cited UNITED STATES PATENTS 1,758,351 5/1930 Cambell 23--154 X 2,271,866 2/1942 Liston 23-154 2,402,978 7/ 1946 Allen 23-154 2,558,011 6/1951 Sprauer 23-154 2,852,582. 9/ 1958 Stallings 23-154 X 3,192,128 6/ 1965 Brandmair 23-154 X 3,254,048 5/ 1966 Schaub 23-312 X FOREIGN PATENTS 570,870 7/ 1945 Great Britain.

OTHER REFERENCES Wilson: Chemical Engineering, vol. 58, No. 7, Iuly 1951, pp. 284 to 287.

NORMAN YUDKOFF, Primary Examiner.

S. I. EMERY, Assistant Examiner.

U.S. Cl. X.R. 260-671, 674, 705 

